/Engine/Source/Runtime/Engine/Public/AnimationRuntime.h
Fill with retarget base ref pose but this isn't used during run-time, so it always copies all of them
static void FillWithRetargetBaseRefPose ( [FCompactPose](API\Runtime\Engine\FCompactPose) & OutPose, const [USkeletalMesh](API\Runtime\Engine\Engine\USkeletalMesh) * Mesh )